Build in democracy
Democratic structures at the start
At the beginning of organising, you and others have likely self-nominated to get things going. This might involve taking responsibility for things like creating and administering the WhatsApp group chat, organising a meeting, or writing some early emails. Good initiative!
In the beginning, since no one wields any outsized power, you are free to do things like this. Moving forwards, though, you may find that you hold key infrastructure like the WhatsApp, or data like a mailing list, or people rely on you to make decisions. As you accumulate this power, it must become justified by the wider membership. The same goes for anyone else.
Tactic: make power positions temporary
If people are carrying out tasks or holding responsibilities in your group, make sure their roles are temporary.
For example, during a meeting, responsibility-holders might stand up and explain what they have been doing, then offer to rotate the role, or share it, to someone else.
Another example is that, at the end of a meeting, the facilitator could call for a group of volunteers to organise the next meeting. At the next meeting, they would be thanked and then that organising role would dissolve.
The same goes principle can apply to organising committee: make them temporary while Your Party is in its early stages and constitutional form is not yet decided.
Tactic: formally elect people to power positions
In some cases, a group of people may have held on to the power to decide when meetings happen, manage the WhatsApp group chat and hold on to data.
If this is the case, it's time to formally elect people to power positions. For example, you could convince the people in a meeting to call for nominations and a vote on the organising committee, with the objective of justifying who is in power.
Tactic: give power-holders a term-limits
If your proto-branch has developed a constitution, you could include a clause that gives power-holders a term-limit. You could also put in a rule that if you are on a proto-committee now, you cannot stand in any formal party roles for a period of 1 year.